Military options for college students?

So I am about to start my junior year in college as a double major of pre-engineering and mathematics with an education minor. I was wondering, other than OCS or OTS and ROTC, what options would the miltary have for me? Enlisted or officer. Are there advanced rankings? Is there a special corps for mathematicians/engineers/scientists? *Duh army corps of engineers* So nevermind I guess include ROTC and OCS too if they are required for a special position. I guess I am looking to sign on to be a scientist/mathematician/engineer/researc… exclusively and not have to go through and be placed based on accessions. Thanks Y.A.